Improving padding/spacing in malcontent-control UI

See #11 (comment 420130). All the points there have been addressed except the padding. Quoting @aday:

One final point: the layout of the parental controls window looks a bit off in general. The spacing is very tight and is uneven in places. Also, I know that it was taken from the user settings, but the user switcher and the panel below don't seem quite right - the spacing around the avatars is uneven, and and the foregrounding of the section at the bottom maybe doesn't feel quite right. As a first step, I'd suggest adjusting the spacing, so there's more of it, and so it's balanced: